Ironing may be described as the process of using an iron to remove wrinkles from a fabric, in particular a garment. During ironing, the fabric may preferably be heated to loosen the intermolecular bonds between the long-chain polymer molecules in the fibers of the fabric. In their loosened condition the weight of the iron may force the fibers in a wrinkle-free state. When the stress in the fibers is properly removed the wrinkle-free state of the fabric will be maintained upon cooling. The removal of stress in the fibers of the fabric is significantly enhanced by heating the fabric to above its glass transition temperature. For many natural fabrics, such as cotton, wool and linen, the glass transition temperature is dependent on the moisture content. The dependency is such that an increase in the moisture content or humidity lowers the transition temperature. A higher moisture content thus improves the degree of stress relaxation, and hence the ironing result at the same temperature. To achieve optimum ironing results, a moisture content of about 3-15% by weight of the fabric to be ironed is desired. The precise optimum percentage depends on the nature of the fabric, and may for example be relatively low for polyester while it is relatively high for natural materials such as cotton.
A fabric being ironed may be moisturized in different ways, such as through steam or liquid water. Steam may for example be released through steam outlet openings in a heated soleplate of the iron, and moisturize the fabric by subsequently condensing therein. A significant drawback of this approach is that steam is not a very efficient moisturizer: only a small fraction of the steam, typically on the order of several tens of percent, is used for moisturizing the fabric; the rest passes through it without condensing. As a result, steam irons are generally incapable of effecting the aforementioned optimum moisture content in the fabric.
It may therefore be advantageous to use an iron that employs liquid water to moisturize a fabric, such as the iron disclosed by U.S. Pat. No. 6,035,563 (Hoefer et al.). The soleplate of the disclosed iron is provided with at least one mist outlet opening, arranged in an area of the soleplate tip. The mist outlet opening allows a liquid stored in a liquid tank to pass through and moisten materials to be ironed. The liquid exits the opening in the form of liquid droplets that are generated using an atomizer device in the form of a piezo-electrically driven thin membrane plate disposed just above the soleplate.
Placement of a piezo-driven membrane just above the soleplate of an iron, as in U.S. '563, is generally prompted by the fact that such atomizers generate a rather local mist. As the water droplets of the mist are imparted with little momentum upon generation, the atomizer must be located close to the fabric being ironed, and thus close the soleplate of the iron. Unfortunately, positioning an atomizer adjacent the soleplate entails a number of drawbacks. Heat from the soleplate, for example, may interfere with its operation. At elevated temperatures the atomization rate may increase unintentionally, while the piezoelectric transducer may even be irreversibly damaged when it is accidentally heated to above its Curie temperature. Furthermore, heat from the soleplate may evaporate the mist that tends to linger around the atomizer even before its droplets reach the fabric being ironed, and consequently reduce the moisturization efficiency of the iron. Another drawback stems from the fact that a relatively large membrane area, plus potentially multiple piezoelectric transducers to drive it, may be required to achieve a sufficient and uniform water deposition rate across the soleplate area. These measures may amount to relatively high manufacturing costs and a lower degree of reliability due to the use of extra, typically delicate components.
It is an object of the present invention to provide for an iron that overcomes or alleviates one or more of these disadvantages associated with known liquid water moisturization irons.